io.wcm.caravan.io.jsontransform.source.JacksonStreamSource.java Source code

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Here is the source code for io.wcm.caravan.io.jsontransform.source.JacksonStreamSource.java

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/*
 * #%L
 * wcm.io
 * %%
 * Copyright (C) 2014 wcm.io
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */
package io.wcm.caravan.io.jsontransform.source;

import io.wcm.caravan.io.jsontransform.element.JsonElement;

import java.io.IOException;
import java.io.InputStream;
import java.math.BigDecimal;

import org.osgi.annotation.versioning.ProviderType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;

/**
 * JSON source using the Jackson streaming parser.
 */
@ProviderType
public final class JacksonStreamSource implements Source {

    private static final Logger LOG = LoggerFactory.getLogger(JacksonStreamSource.class);

    private static final JsonFactory JSON_FACTORY = new JsonFactory();
    private final JsonParser parser;

    private JsonElement current;

    /**
     * @param input The input stream
     * @throws JsonParseException Error reading json
     * @throws IOException Error reading stream
     */
    public JacksonStreamSource(final InputStream input) throws JsonParseException, IOException {
        parser = JSON_FACTORY.createParser(input);
    }

    @Override
    public boolean hasNext() {
        parseJsonElementIfNeeded();
        return current != null;
    }

    @Override
    public JsonElement next() {
        parseJsonElementIfNeeded();
        JsonElement next = current;
        current = null;
        return next;
    }

    private void parseJsonElementIfNeeded() {
        if (current == null) {
            try {
                JsonToken token = parser.nextToken();
                if (token != null) {
                    current = parseJsonElement(token);
                }
            } catch (IOException ex) {
                LOG.error("Error reading JSON stream", ex);
            }
        }
    }

    private JsonElement parseJsonElement(final JsonToken token) throws IOException {
        String key = parser.getCurrentName();
        if (JsonToken.START_OBJECT.equals(token)) {
            return JsonElement.DEFAULT_START_OBJECT;
        } else if (JsonToken.END_OBJECT.equals(token)) {
            return JsonElement.DEFAULT_END_OBJECT;
        } else if (JsonToken.START_ARRAY.equals(token)) {
            return JsonElement.DEFAULT_START_ARRAY;
        } else if (JsonToken.END_ARRAY.equals(token)) {
            return JsonElement.DEFAULT_END_ARRAY;
        } else if (JsonToken.FIELD_NAME.equals(token)) {
            return handleFieldName(key);
        }
        return JsonElement.value(key, parseValue(token));
    }

    private JsonElement handleFieldName(String key) throws IOException, JsonParseException {
        JsonToken next = parser.nextToken();
        if (JsonToken.START_OBJECT.equals(next)) {
            return JsonElement.startObject(key);
        } else if (JsonToken.START_ARRAY.equals(next)) {
            return JsonElement.startArray(key);
        } else {
            return JsonElement.value(key, parseValue(next));
        }
    }

    private Object parseValue(final JsonToken token) throws IOException {
        if (token.isBoolean()) {
            return parser.getBooleanValue();
        } else if (token.isNumeric()) {
            return new BigDecimal(parser.getText());
        } else {
            return parser.getText();
        }
    }

    @Override
    public void close() throws IOException {
        parser.close();
    }

}